A simple, task-oriented notation for describing user actions in asynchronous user interfaces is introduced. This User Action Notation (UAN) allows the easy association of actions with feedback and system state changes as part of a set of asynchronous interface design techniques, by avoiding the verbosity and potential vagueness of prose. Use within an actual design and implementation project showed the UAN to be expressive, concise, and highly readable because of its simplicity. The task-and user-oriented techniques are naturally asynchronous and a good match for object-oriented implementation. Levels of abstraction are readily applied to allow definition of primitive tasks for sharing and reusability and to allow hiding of details for chunking. The UAN provides a critical articulation point, bridging the gap between the task viewpoint of the behavioral domain and the event-driven nature of the object-oriented implementational domain. The potential for UAN task description analysis may address some of the difficulties in developing asynchronous interfaces.